Density Functional Theory Study on the Structure and Capillary Phase Transition of a Polymer Melt in a Slitlike Pore:  Effect of Attraction

Abstract

A density functional theory is proposed to investigate the effects of polymer monomer-monomer and monomer-wall attractions on the density profile, chain configuration, and equilibrium capillary phase transition of a freely jointed multi-Yukawa fluid confined in a slitlike pore. The excess Helmholtz energy functional is constructed by using the modified fundamental measure theory, Wertheim's first-order thermodynamic perturbation theory, and Rosenfeld's perturbative method, in which the bulk radial distribution function and direct correlation function of hard-core multi-Yukawa monomers are obtained from the first-order mean spherical approximation. Comparisons of density profiles and bond orientation correlation functions of inhomogeneous chain fluids predicted from the present theory with the simulation data show that the present theory is very accurate, superior to the previous theory. The present theory predicts that the polymer monomermonomer attraction lowers the strength of oscillations for density profiles and bond orientation correlation functions and makes the excess adsorption more negative. It is interesting to find that the equilibrium capillary phase transition of the polymeric fluid in the hard slitlike pore occurs at a higher chemical potential than in bulk condition, but as the attraction of the pore wall is increased sufficiently, the chemical potential for equilibrium capillary phase transition becomes lower than that for bulk vapor-liquid equilibrium.

Attractive hard-core Yukawa fluids in the nanosized pores: Structure and phase behaviors

“…The advantage of this theory is the simplicity of the calculation of the long-range attraction or repulsive interactions. In the previous paper [25], Kim et al have shown that (i) this method is better than the other approximations [18][19][20][21][22][23], which are based on the Taylor density functional expansion with respect to the bulk density, and that (ii) the calculated particle density distributions as well as the thermodynamics are in an excellent agreement with the computer simulation in the wide range of density at the subcritical temperature. In this paper, we extend this method for studying the structure and phase behaviors of an attractive HCY fluid in the nanosized pores.…”

“…The reasons are that (i) many studies had been carried out to investigate the structure and phase behaviors of a bulk HCY fluid [6][7][8][9][10][11][12][13][14][15][16] due to its ability to represent many real fluid system from simple to complex fluids such as charge-stabilized colloidal suspension, micells, protein, and microemulsions, (ii) a few work are done on the structure of an attractive HCY fluid at interfaces [17][18][19][20][21][22][23][24][25], and that (iii) as far as the authors know, the phase behaviors of an attractive HCY fluid at the subcritical temperature, which is confined in the nanopores such as the slit and spherical pores, have not been reported until now. The attractive HCY potential is given by the following expression…”

Density functional study of pressure profile for hard-sphere fluids confined in a nano-cavity

“…Recently, the density functional theory 15,16 for hard-sphere fluids, especially fundamental measure theory (FMT) 17 and its modified version, 18 has been widely employed in the study of Lennard-Jones fluids, 19 Yukawa fluids, 20 chain fluids 21 and electrolyte solutions. 22,23 Rich information about the structural and thermodynamic properties of these systems has been well predicted by using the hard-sphere reference system.…”

A hybrid perturbed-chain SAFT density functional theory for representing fluid behavior in nanopores: Mixtures

“…4 A variety of DFT models have been developed to predict the properties of inhomogeneous simple atomic and complex fluids, and those based on Wertheim's first order thermodynamic perturbation theory (TPT1) are promising. [4][5][6][7] For example, Yu et al 8 developed a DFT based on Wertheim's TPT1 for chain conformation and bond orientation correlation function of hard-core multi-Yukawa chain fluids. Borouko et al 9 proposed a DFT to study the phase behavior of a two-component fluid in a slit-like pore with walls modified by tethered chains.…”